Saldaña was on the founding Board of Directors for San Diego Earth Day and organized the first "Earth Fair" in Balboa Park in 1990. She was chair of the San Diego chapter of the Sierra Club from Jan. 1996 to Aug. 1997 and served in other volunteer positions for the Club. Her main interests were in water reclamation and sewage treatment, especially along the US-Mexico border. She served as Chair of the San Diego Wetlands Advisory Board 1992-94. President Clinton appointed her in 1999 to the Border Environment Cooperation Commission's Advisory Council.

In 2004, incumbent State Assemblywoman Christine Kehoe of California's 76th State Assembly district decided to retire in order to run for a seat in the California Senate. Saldaña ran for the open seat and won the Democratic primary with a plurality of 41% of the vote.[1] In the general election, she defeated Republican Tricia Hunter, a former Assemblywoman, 54%-41%.[2] In 2006, she won re-election to a second term with 64% of the vote.[3] In 2008, she won re-election to a third term with 64% of the vote.[4] She left the Assembly due to term limits in 2010.

In 2007 Saldaña was named Legislator of the Year by Californians Against Waste for her legislation regarding E-waste. Capitol Weekly, California's major weekly periodical covering the state legislature, publishes an annual legislative scorecard to pin down the political or ideological leanings of every member of the legislature based on how they voted on an assortment of bills in the most recent legislative session. On the scorecard, "100" is a perfect liberal score and "0" is a perfect conservative score.,[5][6] On the 2009 Capitol Weekly legislative scorecard, Saldana ranked as a 97.[7]

Saldana is a staunch advocate of environmental legislation. She co-authored the Global Warming Solutions Act (AB 32), which sought to reduce greenhouse gas emissions while instituting renewable energy mandates. She also sought to decrease the use of fossil fuels while making solar energy more affordable by co-authoring the Million Dollar Solar Initiative. Additionally, she authored legislation to increase California's Environmental Fund, which included increasing the use of hybrid vehicles and reduced-emission buses.

In the 2009 session of the state legislature, Saldana introduced three bills that would restrict California's ballot initiative process:

Assembly Bill 6, which would require petition drive management companies to pay an annual fee and register with the California Secretary of State

Assembly Bill 426, which would increase the fee that proponents of an initiative measure are required to pay at the time of submitting the draft of the measure to the Attorney General from $200 to $2,000.

Assembly Bill 1068, which would forbid contracts with signature gatherers premised upon whether or not the measure qualifies for the ballot.[8]

Due to California's term limits, Saldaña's assembly career ended on August 31, 2010 in an acrimonious late-night session as she pushed legislation banning the open carry of firearms known as AB 1934.[9] Saldaña presented her bill to the Assembly with 70 minutes remaining in the 2010 regular session, and would not suspend debate when it became clear that its opponents would not let it come to an early vote.[10] Saldaña later clashed with fellow Democrats over their refusal to employ parliamentary procedure tactics to end debate so her measure could be heard.[11]

In January 2016 she announced her candidacy for the mayor of San Diego against incumbent mayor Kevin Faulconer in his bid for re-election.[12][13] For this election, she ran with a party affiliation of "no preference," though the office of mayor is officially nonpartisan.[12] She lost in the primary to Faulconer, coming in second.

In 2018, Saldaña ran for a seat on the officially nonpartisan San Diego County Board of Supervisors. She campaigned as a Democrat, having changed her party affiliation back after the mayoral election.[14] She came in third place in the open primary and did not advance to the general election, which was ultimately won by Nathan Fletcher.[15]